The present invention relates to a vehicle bumper system for improved bending strength, impact resistance, and pedestrian safety, and more particularly relates to a structural beam having a multi-concavity-defining cross section or an S-shaped cross section across a substantial length of the beam. The beam is particularly useful for primary beams in low weight vehicles and/or as a compliment to the vehicle's primary beam in a pedestrian impact application. The present beam is not believed to be limited to only vehicle front bumpers, nor to only pedestrian safety, but is believed relevant to any structural impact beam where the beam's shape, bending strength, and impact energy absorption during impact/bending is important.
Historically, vehicle front bumper systems were intended to protect vehicles from damage, as well as reduce injury to vehicle passengers. Recently, there has been increased attention directed to pedestrian safety, and in particular to a reduction to leg injury upon being struck by a vehicle. Further, there continues to be very strong competitive pressures to reduce overall cost to bumper systems, to minimize the number and weight of components, and to optimize and distribute energy absorption over an impact stroke, while at the same time maintaining design flexibility and adaptability.
Several factors are important for beams intended for impact resistance and energy absorption. For example, a beam's impact strength to weight ratio is important in order to provide optimal beam strength yet minimum vehicle weight. Also, “efficiency” of the energy absorption is important, where the beam quickly reaches a predetermined value upon being impacted, and then maintains that resistance level for a period of time, yet where peaks and valleys of loading are avoided, and where energy absorption is made predictable and consistent.